Connect server

The client can use the endpoints returned by DNS query to connect server application. The following is an example: 

  1. #include <boost/asio.hpp>
  2. #include <iostream>
  4. int main()
  5. {
  6.     try
  7.     {
  8.         boost::asio::io_context io_context;
  10.         boost::asio::ip::tcp::resolver resolver{io_context};
  11.         boost::asio::ip::tcp::resolver::results_type endpoints =
  12.                 resolver.resolve("google.com", "https");
  14.         boost::asio::ip::tcp::tcp::socket socket{io_context};
  15.         auto endpoint = boost::asio::connect(socket, endpoints);
  17.         std::cout << "Connect to " << endpoint << " successfully!\n";
  18.     }
  19.     catch (std::exception& e)
  20.     {
  21.         std::cerr << e.what() << '\n';
  22.         return -1;
  23.     }
  25.     return 0;
  26. }

The running result is like following: 

  1. Connect to 172.217.194.101:443 successfully!

Please notice boost::asio::connect requires the iterator of endpoints. If you just want one specified endpoint, you can use connect member function of socket. Check following code: 

  1. #include <boost/asio.hpp>
  2. #include <iostream>
  4. int main()
  5. {
  6.     try
  7.     {
  8.         boost::asio::io_context io_context;
  10.         boost::asio::ip::tcp::resolver resolver{io_context};
  11.         boost::asio::ip::tcp::resolver::results_type endpoints =
  12.                 resolver.resolve("google.com", "https");
  14.         boost::asio::ip::tcp::tcp::socket socket{io_context};
  15.         auto eit = endpoints.cbegin();
  16.         for (; eit != endpoints.cend(); eit++)
  17.         {
  18.             boost::system::error_code ec;
  19.             boost::asio::ip::tcp::endpoint endpoint = *eit;
  20.             socket.connect(endpoint, ec);
  21.             if (!ec)
  22.             {
  23.                 std::cout << "Connect to " << endpoint << " successfully!\n";
  24.                 break;
  25.             }
  26.         }
  28.         if (eit == endpoints.cend())
  29.         {
  30.             std::cout << "Connect failed!\n";
  31.             return  -1;
  32.         }
  33.     }
  34.     catch (std::exception& e)
  35.     {
  36.         std::cerr << e.what() << '\n';
  37.         return -1;
  38.     }
  40.     return 0;
  41. }

The running result is like this: 

  1. Connect to 172.217.194.139:443 successfully!